The present invention relates to novel complexes in which amorphous calcium phosphates are stabilised by phosphopeptides. These complexes have anti-cariogenic effects, and may also be used as dietary supplements to increase calcium bioavailability and to heal or prevent diseases associated with calcium deficiencies. Methods of making the complexes of the invention and of treatment or prevention of dental caries, calcium malabsorption, and bone diseases are also provided
Dental caries is initiated by the demineralisation of hard tissue on the teeth by organic acids produced from fermentation of dietary sugar by dental plaque odontopathogenic bacteria
Even though the prevalence of dental caries has deceased through the use of fluoride in most developed countries, the disease =as a major public health problem. The estimated economic burden of treating dental caries in Australia in 1991 was $471 million, being higher an that for other diet-related diseases including coronary heart disease, hypertension or stroke.
In developing countries where the availability of industrialised food products is increasing, prevalence of dental caries is also increasing. Recent studies have highlighted a number of socio-demographic variables associated with the risk of developing caries; high risk is associated with ethnicity and low socio-economic status. The level of high-risk individuals has remained constant even though the overall severity and prevalence of disease in the community has decreased. Dental caries is therefore, still a major public health problem, particularly in ethnic and lower socioeconomic groups. This highlights the need for a non-toxic, anticariogenic agent that could supplement the effects of fluoride to fit lower the incidence of dental caries. An agent which would reduce the dose of fluoride required to reduce the incidence of caries would be particularly desirable in view of community anxiety about fluoride, and in view of the fact that fluorosis can develop even at currently used doses.
The food group most recognised as exhibiting anticaries activity is dairy products (milk, milk concentrates, powders and cheeses). U.S. Pat. No. 5,130,123 discloses the component responsible for this anticariogenic activity as casein. However, the use of casein as an anticariogenic agent is precluded by adverse organoleptic properties and the very high levels required for activity.
Preliminary investigations determined that tryptic casein phosphopeptides contributed to the anticariogenic activity and this was made subject of U.S. Pat. No. 5,015,628. In particular, peptides Bos xcex1s1-casein X-5P (f59-79) (SEQ ID NO: 1, Bos xcex2-casein X-4P (f1-25) (SEQ ID: NO: 2), Bos xcex1s2-casein X-4P (f46-70) (SEQ ID NO: 3) and Bos xcex1s2-casein X-4P (f1-21) (SEQ ID NO: 4) were disclosed in U.S. Pat. 5,015,628 as follows:
(SEQ ID NO: 1) Gln59-Met-Glu-Ala-Glu-Ser(P)-Ile-Ser(P)-Ser(P)-Ser(P)-Glu-Ile-Val-Pro-Asn-Ser(P)-Val-Glu-Gln-Lys79. xcex1s1(59-79)
(SEQ ID NO: 2) Arg1-Glu-Leu-Glu-Glu-Leu-Asn-Val-Pro-Gly-Glu-Ile-Val-Glu-Ser(P)-Leu-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-Ser-Ile-Thr-Arg25. xcex2(1-25)
(SEQ ID NO: 3) Asn46-Ala-Asn-Glu-Glu-Glu-Tyr-Ser-Ile-Gly-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-Ser(P)-Ala-Glu-Val-Ala-Thr-Glu-Glu-Val-Lys70. xcex1s2(46-70)
(SEQ ID NO: 4) Lys1-Asn-Thr-Met-Glu-His-Val-Ser(P)-Ser(P)-Ser(P)-Glu-Glu-Ser-Ile-Ile-Ser(P)-Gln-Glu-Thr-Tyr-Lys21. xcex1s2(1-21)
The preliminary determination of the above phosphopeptides for use in combination with CaHPO4 and hydroxyaptite provided novel peptides having anticariogenic properties. However, subsequent investigations have determined that the Ser(P) cluster sequence motif within the previous disclosed phosphopeptides have the unexpected ability to stabilize their own weight in amorphous calcium phosphate. The ability of the above phosphopeptides and in particular the Ser(P) motif to stabilise amorphous calcium phosphate was quite unexpected and neither disclosed or taught in any publications known to the Applicants. We have now found that the amorphous form of calcium phosphate Ca3(PO4)1.87(HPO4)0.2xH2O where xxe2x89xa71 stabilised by the casein phosphopeptides is the most soluble, basic form of non-crystalline calcium phosphate and a superior form of calcium phosphate which prevents caries and increases calcium bioavailability. Amorphous calcium phosphate (ACP) must be formed by careful titration of Ca ions (eg CaCl2) and phosphate ions (eg Na HPO4) while maintaining the pH above 7 (preferably 9.0) in the presence of the phosphopeptide. As the ACP is formed, the phosphopeptide binds to the nascent nuclei and stabilises the ACP as a phosphopeptide-ACP complex. Without the phosphopeptide, the ACP will precipitate out of solution and transform within minutes into, the most stable calcium phosphate phase, crystalline hydroxyapatite (HA). HA, by being insoluble has limited anticariogenic activity and presents calcium in a poorly bioavailable form. The acidic phase of calcium phosphate CaHPO4, while certainly being more soluble than hydroxyapatite, is poorly bound by the phosphopeptide and poorly localised at the tooth surface and therefore also has limited anticariogenic activity. The unexpected ability of the aforementioned phosphopeptides and in particular Ser(P) cluster motif to stabilize amorphous calcium phosphate was not disclosed or taught in U.S. Pat. No. 5,015,628 and provides for the first time a reliable and effective method of producing a stabilized amorphous calcium phosphate complex having distinct and novel advantages in calcium treatments and delivery. U.S. Pat. No. 5,015,628 does not disclose the unique amorphous calcium fluoride phosphate phase Ca8(PO4)5F x H2O where xxe2x89xa71 which we have now found to be stabilised by the above phosphopeptides and can be localised at the tooth surface to provide superior anticaries efficacy. This unexpected ability to stabilize amorphous calciun phosphate forms the basis of the instant invention.
In one aspect, the invention provides a stable calcium phosphate complex, comprising amorphous calcium phosphate or a derivative thereof stabilized by a phosphopeptide, wherein said phosphopeptide comprises the sequence Ser(P)-Ser(P)-Ser(P)-Glu-Glu-(SEQ ID NO: 5).
In one embodiment, the complex may include phosphopeptide stabilized amorphous calcium fluoride phosphate.
The phosphopeptide (PP) may be from any source; it may be obtained by tryptic digestion of casein or other phospho-acid rich proteins such as phosphitin, or by chemical or recombinant synthesis, provided that it comprises the core sequence -Ser(P)-Ser(P)-Ser(P)-Glu-Glu-(SEQ ID NO: 5). The sequence flanking this core sequence may be any sequence. However, those flanking sequences in xcex1s1(59-79) (SEQ ID NO: 1), xcex2(1-25) (SEQ ID NO: 2), xcex1s2(46-70 (SEQ ID NO: 3) and xcex1s2(1-21) (SEQ ID NO: 4) are preferred. The flanking sequences may optionally be modified by deletion, addition or conservative substitution of one or more residues. The amino acid composition and sequence of the flanking region are not critical as long as the conformation of the peptide is maintained and that all phosphoryl and carboxyl groups interacting with calcium ions are maintained as the preferred flanking regions appear to contribute to the structural action of the motif.
When the complex takes the form of phosphopeptide stabilized amorphous calcium fluoride phosphate, the calcium fluoride phosphate may be of the approximate formula [Ca(PO4)5 Fx H2O] wherein xxe2x89xa71.
The complex may firer include HPO4 as a minor optional component to the complex. The HP04 is believed to act as a coating for the ACP cluster. When the complex takes the alternative form of a stable soluble alkaline calcium phosphate complex including stabilized amorphous calcium phosphate, the amorphous calcium phosphate may be of the approximate formula [Ca3(PO4)2 x H2O] wherein xxe2x89xa71.
The complex may firther include HPO4 as a minor optional component. The complex most preferably has a pH of about 9.0.
The phosphopeptide (PP) may be from any source; it may be obtained by tryptic digestion of casein or other phospho-acid rich proteins such as phosphitin, or by chemical or recombinant synthesis, provided that it comprises the core sequence -Ser(P)-Ser(P)-Ser(P)-Glu-Glu-. The sequence flanking this core sequence may be any sequence. However, those flanking sequences in xcex1s1(59-79) [1], xcex2(1-25) [2], xcex1s2(46-70) [3] and xcex1s2(1-21) [4] are preferred. The flanking sequences may optionally be modified by deletion, addition or conservative substitution of one or more residues. The amino acid composition and sequence of the flanking region are not critical as long as the conformation of the peptide is maintained and that all phosphoryl and carboxyl groups interacting with calcium ions are maintained as the preferred flanking regions appear to contribute to the structural action of the motif.
The complex formed preferably has the formula [(PP)(CP)8]n where n is equal to or greater than 1, for example, 6. The complex formed may be a colloidal complex.
The phosphopeptide binds to the ACP cluster to produce a metastable solution in which growth of ACP to a size that initiates nucleation and precipitation is prevented. In this way, calcium and other ions such as fluoride ions can be localised, for instance at a surface on a tooth to prevent demineralisation and prevent formation of dental caries.
Thus, in a second aspect, the invention provides a stable calcium phosphate complex as described above, which complex acts as a delivery vehicle that co-localises ions including, but not limited to calcium, fluoride and phosphate ions at a target site. In a preferred embodiment, the complex is in a slow-release amorphous form that produces superior anti-caries efficacy.
In a particularly preferred embodiment of the invention, the stable calcium complex is incorporated into dentifrices such as toothpaste, mouth washes or formulations for the mouth to aid in the prevention and/or treatment of dental caries or tooth decay. The calcium complex may comprise 0.05-50% by weight of the composition, preferably 1.0-50%. For oral compositions, it is preferred that the amount of the CPP-ACP and/or CPP-ACFP administered is 0.05-50% by weight, preferably 1.0%-50% by weight of the composition. The oral composition of this invention which contains the above-mentioned agents may be prepared and used in various forms applicable to the mouth such as dentifrice including toothpastes, toothpowders and liquid dentifrices, mouthwashes, troches, chewing gums, dental pastes, gingival massage creams, gargle tablets, dairy products and other foodstuffs. The oral composition according to this invention may flirter include additional well known ingredients depending on the type and form of a particular oral composition.
In certain highly preferred forms of the invention the oral composition may be substantially liquid in character, such as a mouthwash or rinse. In such a preparation the vehicle is typically a water-alcohol mixture desirably including a humnectant as described below. Generally, the weight ratio of water to alcohol is in the range of from about 1:1 to about 20:1. The total amount of water-alcohol mixture in this type of preparation is typically in the range of from about 70 to about 99.9% by weight of the preparation. The alcohol is typically ethanol or isopropanol. Ethanol is preferred.
The pH of such liquid and other preparations of the invention is generally in the range of from about 5 to about 9 and typically from about 7.0-9.0. The pH can be controlled with acid (e.g. citric acid or benzoic acid) or base (e.g. sodium hydroxide) or buffered (as with sodium citrate, benzoate, carbonate, or bicarbonate, disodium hydrogen phosphate, sodium dihydrogen phosphate, etc).
In other desirable forms of this invention, the oral composition may be substantially solid or pasty in character, such as toothpowder, a dental tablet or a toothpaste (dental cream) or gel dentifrice. The vehicle of such solid or pasty oral preparations generally contains dentally acceptable polishing material. Examples of polishing materials are water-insoluble sodium metaphosphate, potassium metaphosphate, tricalcium phosphate, dihydrated calcium phosphate, anhydrous dicalcium phosphate, calcium pyrophosphate, magnesium orthophosphate, trimagnesium phosphate, calcium carbonate, hydrated alumina, calcined alumina, aluminum silicate, zirconium silicate, silica, bentonite, and mixtures thereof. Other suitable polishing material include the particulate thermosetting resins such as melamine-, phenolic, and urea-formaldehydes, and cross-linked polyepoxides and polyesters. Preferred polishing materials include crystalline silica having particle sized of up to about 5 microns, a mean particle size of up to about 1.1 microns, and a surface area of up to about 50,000 cm2/gm., silica gel or colloidal silica, and complex amorphous alkali metal aluminosilicate.
When visually clear gels are employed, a polishing agent of colloidal silica, such as those sold under the trademark SYLOID as Syloid 72 and Syloid 74 or under the trademark SANTOCEL as Santocel 100, alkali meal alumino-silicate complexes are particularly usefull since they have refractive indices close to the refractive indices of gelling agent-liquid (including water and/or humectant) systems commonly used in dentifrices.
Many of the so-called xe2x80x9cwater insolublexe2x80x9d polishing materials are anionic in character and also include small amounts of soluble material. Thus, insoluble sodium metaphosphate may be formed in any suitable manner as illustrated by Thorpe""s Dictionary of Applied Chemistry, Volume 9, 4th Edition, pp. 510-511. The forms of insoluble sodium metaphosphate known as Madrell""s salt and Kurrol""s salt are farther examples of suitable materials. These metaphosphate salts exhibit only a minute solubility in water, and therefore are commonly referred to as insoluble metaphosphates (IMP). There is present therein a minor amount of soluble phosphate material as impurities, usually a few percent such as up to 4% by weight. The amount of soluble phosphate material, which is believed to include a soluble sodium trimetaphosphate in the case of insoluble metaphosphate, may be reduced or eliminated by washing with water if desired The insoluble alkali metal metaphosphate is typically employed in powder form of a particle size such that no more than 1% of the material is larger than 37 microns.
The polishing material is generally present in the solid or pasty compositions in weight concentrations of about 10% to about 99%. Preferably, it is present in amounts from about 10% to about 75% in toothpaste, and from about 70%/o to about 99% in toothpowder. In toothpastes, when the polishing material is silicious in nature, it is generally present in amount of about 10-30% by weight, Other polishing materials are typically present in amount of about 30-75% by weight.
In a toothpaste, the liquid vehicle may comprise water and humectant typically in an amount ranging from about 10% to about 80% by weight of the preparation. Glycerine, propylene glycol, sorbitol and polypropylene glycol exemplify suitable humectants/carriers. Also advantageous are liquid mixtures of water, glycerine and sorbitol. In clear gels where the refractive index is an important consideration, about 2.5-30% w/w of water, 0 to about 70% w/w of glycerine and about 20-80% w/w of sorbitol are preferably employed.
Toothpaste, creams and gels typically contain a natural or synthetic thickener or gelling agent in proportions of about 0.1 to about 10, preferably about 0.5 to about 5% w/w. A suitable thickener is synthetic hectorite, a synthetic colloidal magnesium alkali metal silicate complex clay available for example as Laponite (e.g. CP, SP 2002, D) marketed by Laporte Industries Limited. Laponite D is, approximately by weight 58.00% SiO2, 25.40% MgO, 3.05% Na2O, 0.98% Li2O, and some water and trace metals. Its true specific gravity is 2.53 and it has an apparent bulk density of 1.0 g/ml at 8% moisture.
Other suitable thickeners include Irish moss, iota carrageenan, gum tragacanth, starch, polyvinylpyrrolidone, hydroxyethylpropylcellulose, hydroxybutyl methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl cellulose (e.g. available as Natrosol), sodium carboxymethyl cellulose, and colloidal silica such as finely ground Syloid (e.g. 244). Solubilizing agents may also be included such as humectant polyols such propylene glycol, dipropylene glycol and hexylene glycol, cellosolves such as methyl cellosolve and ethyl cellosolve, vegetable oils and waxes containing at least about 12 carbons in a straight chain such as olive oil, castor oil and petrolatum and esters such as amyl acetate, ethyl acetate and benzyl benzoate.
It will be understood that, as is conventional, the oral preparations are to be sold or otherwise distributed in suitable labelled packages. Thus, a jar of mouthrinse will have a label describing it, in substance, as a mouthrinse or. mouthwash and having directions for its use; and a toothpaste, cream or gel will usually be in a collapsible tube, typically aluminium, lined lead or plastic, or other squeeze, pump or pressurized dispenser for metering out the contents, having a label describing it, in substance, as a toothpaste, gel or dental cream.
Organic surface-active agents are used in the compositions of the present invention to achieve increased prophylactic action, assist in achieving thorough and complete dispersion of the active agent throughout the oral cavity, and render the instant compositions more cosmetically acceptable. The organic surface-active material is preferably anionic, nonionic or ampholytic in nature and preferably does not interact with the active agent. It is preferred to employ as the surface-active agent a detersive material which imparts to the composition detersive and foaming properties. Suitable examples of anionic surfactants are water-soluble salts of higher fatty acid monoglyceride monosulfates, such as the sodium salt of the monosulfated monoglyceride of hydrogenated coconut oil fatty acids, higher alkyl sulfates such as sodium lauryl sulfite, alkyl aryl sulfonates such as sodium dodecyl benzene sulfonate, higher alkylsulfo-acetates, higher fatty acid esters of 1,2-dihydroxy propane sulfonate, and the substantially saturated higher aliphatic acyl amides of lower aliphatic amino carboxylic acid compounds, such as those having 12 to 16 carbons in the fatty acid, alkyl or acyl radicals, and the like. Examples of the last mentioned amides are N-lauroyl sarcosine, and the sodium, potassium, and ethanolamine salts of N-lauroyl, N-myristoyl, or N-palmitoyl sarcosine which should be substantially free from soap or similar higher fatty acid material. The use of these sarconite compounds in the oral compositions of the present invention is particularly advantageous since these materials exhibit a prolonged marked effect in the inhibition of acid formation in the oral cavity due to carbohydrates breakdown in addition to exerting some reduction in the solubility of tooth enamel in acid solutions. Examples of water-soluble nonionic surfactants suitable for use are condensation products of ethylene oxide with various reactive hydrogen-containing compounds reactive therewith having long hydrophobic chains (e.g. aliphatic chains of about 12 to 20 carbon atoms), which condensation products (xe2x80x9cethoxamersxe2x80x9d) contain hydrophilic polyoxyethylene moieties, such as condensation products of poly (ethylene oxide) with fatty acids, fatty alcohols, fatty amides, polyhydric alcohols (e.g. sorbitan monostearate) and polypropyleneoxide (e.g. Pluronic materials).
The surface active agent is typically present in amount of about 0.1-5% by weight. It is noteworthy, that the surface active agent may assist in the dissolving of the active agent of the invention and thereby diminish the amount of solibilizing humectant need.
Various other materials may be incorporated in the oral preparations of this invention such as whitening agents, preservatives, silicones, chlorophyll compounds and/or ammoniated material such as urea, diammonium phosphate, and mixtures thereof. These adjuvants, where present, are incorporated in the preparations in amounts which do not substantially adversely affect the properties and characteristics desired.
Any suitable flavouring or sweetening material may also be employed. Examples of suitable flavouring constituents are flavouring oils, e.g. oil of spearmint, peppermint, wintergreen, sassafras, clove, sage, eucalyptus, marjoram, cinnamon, lemon, and orange, and methyl salicylate. Suitable sweetening agents include sucrose, lactose, maltose, sorbitol, xylitol, sodium cyclamate, perillartine, AMP (aspartyl phenyl alanine, methyl ester), saccharine, and the like. Suitably, flavour and sweetening agents may each or together comprise from about 0.1% to 5% more of the preparation
In the preferred practice of this invention an oral composition according to this invention such as mouthwash or dentifrice containing the composition of the present invention is preferably applied regularly to the gums and teeth, such as every day or every second or third day or preferably from 1 to 3 times daily, at a pH of about 4.5 to about 9, generally about 7.0 to about 9, for at least 2 weeks up to 8 weeks or more up to a lifetime.
The compositions of this invention can also be incorporated in lozenges, or in chewing gum or other products, e.g. by stirring into a warm gum base or coating the outer surface of a gum base, illustrative of which may be mentioned jelutong, rubber latex, vinylite resins, etc., desirably with conventional plasticizers or softeners, sugar or other sweeteners or such as glucose, sorbitol and the like.
In another embodiment, the complex of the invention is formulated to form a dietary supplement preferably comprising 0.1-100% w/w, more preferably 1-50% w/w, most preferably 1-10% and particularly 2% w/w. The complex may also be incorporated into food products.
Accordingly, in a third sect the invention provides compositions including pharmaceutical compositions comprising the calcium complex as described together with a pharmaceutically-acceptable carrier. Such compositions may be selected from the group consisting of dental, anti-cariogenic compositions, therapeutic compositions and dietary supplements. Dental compositions or therapeutic compositions may be in the form of a gel, liquid, solid, powder, cream or lozenge. Therapeutic compositions may also be in the form of tablets or capsules.
In a fourth aspect, there is provided a method of treating or preventing dental caries or tooth decay comprising the step of administering a complex or composition of the invention to the teeth or gums of a subject in need of such treatments. Topical administration of the complex is preferred.
In a fifth aspect, the invention relates to methods of treating one or more conditions related to calcium loss from the body, especially from the bones, calcium deficiency, calcium malabsorption, or the like. Examples of such conditions include, but are not limited to, osteoporosis and osteomalacia. In general any condition which can be improved by calcium bioavailability is contemplated
In a sixth aspect, the invention also provides a method of producing a stable complex of calcium phosphate as described above, comprising the step of:
(i) obtaining a solution of phosphopeptide having a pH of about 9.0;
(ii) admixing (i) with solutions comprising calcium, and inorganic phosphate and optionally fluoride at a pH of about 9.0;
(iii) filtering the mixture resulting from step (ii), and
(iv) drying to obtain the said complex.
The complexes of the invention are useful as calcium supplements in subjects in need of stimulation of bone growth, for example subjects undergoing frature repair, joint replacement, bone grafts, or craniofacial surgery.
These complexes are also useful as dietary supplements m subjects who for any reason, such as dietary intolerance, allergy, or religious or cultural factors, are unable or unwilling to consume dairy products in an amount sufficient to supply their dietary calcium requirements.
It will be clearly understood tat, although this specification refers specifically to applications in humans, the invention is also useful for veterinary purposes. Thus in all aspects the invention is useful for domestic animals such as cattle, sheep, horses and poultry; for companion animals such as cats and dogs; and for zoo animals.